The present invention relates to an electrophotographic copier which has a function of forming life-size copies of documents and of forming modified-size copies, i.e. enlarged or reduced copies of documents.
Various types of such electrophotographic copiers have been known and one of them is shown in FIG. 1. This known copier is of a type in which a traveling document is scanned by a slit type exposing optical system and an image of the document is projected onto a rotating photosensitive drum. A document 1 is placed on a document table 2 consisting of a transparent glass plate and the table 2 is reciprocally moved as shown by a double-headed arrow by means of a suitable driving mechanism not shown. Below the document table 2 is arranged a scanning optical system including an illumination lamp 3 enclosed by a concave reflection mirror 4, plane reflection mirrors 5, 6, 8 and 9 and a projection lens 7. Then an image of the document 1 is projected onto a photosensitive drum 10 by means of the mirrors 5 and 6, the projection lens 7 and the mirrors 8 and 9 to form an electrostatic latent image on the drum 10. The mirrors 5 and 6 and projection lens 7 are arranged movably between positions shown by solid lines and chain lines. When the mirrors 5 and 6 and projection lens 7 are driven in the solid line positions, life-size image of the document 1 is projected, whereas when they are moved into the chain line positions, an enlarged image of the document is projected onto the drum 10. In the known copier, since a plurality of elements such as the mirrors 5, 6 and projection lens 7 have to be moved over a relatively long distance, it is necessary to provide a rather complicated and large driving mechanism and a quite large space is required and thus, the whole construction of the copier is liable to be complicated in construction and large in size. Further, since the driving mechanism becomes large and heavy, there might be produced undesired noise and vibration and moreover, the movement could not be effected speedily.